Where to put external Python Blender scripts when Blender was installed from Snap?
After talking to the guys on the official Blender forum #python it turned out the scrip can be located pretty much anywhere and it doesn't need to be in a special directory, as I thought before. To run it I used a command i.e: blender --background monkey_test.blend --python ./get_scene_framerange.py where the last bit is a path to the script located anywhere